Graphene, which is an aggregate of six-membered ring structures of carbon atoms, has much higher mobility than silicon (Si), for example, mobility of 2,000,000 cm2/Vs in theoretical value, and mobility of 200,000 cm2/Vs in past experimental value. Thus, application of graphene to semiconductor devices, for example, ultrahigh-speed switching devices and high-frequency devices has been studied. In addition, graphene also has a ballistic conduction characteristic. Thus, there have been studies contemplating the use of graphene as a fine-width low-resistance wiring material instead of copper (Cu) in a semiconductor device.
As a method for manufacturing graphene, a method has been used in which a film formation target such as copper or the like is heated to a high temperature, for example, 800 degrees C. or higher. In this method, a carbon source gas is brought into contact with the film formation target and decomposed, and graphene is generated on the surface of the film formation target by the catalytic activity of the film formation target. The graphene manufactured by this manufacturing method is high in quality. However, in order to apply the graphene to an electronic device, it is necessary to separate the graphene from the film formation target and to transfer the graphene to a silicon substrate. Since graphene is a single layered graphite and is very thin, it is difficult to separate the graphene from a large-area silicon substrate or to transfer the graphene to a large-area substrate. Further, in the case of directly manufacturing graphene on a silicon substrate, when heated at a high temperature of 800 degrees C. or higher, elements of an electronic device formed before graphene generation may be destroyed by high temperature heating during the generation of graphene.
Under the foregoing circumstances, a method for manufacturing graphene on a silicon substrate at a relatively low temperature, for example, 500 to 600 degrees C. has been proposed. As such a method for manufacturing graphene at a low temperature, a method has been used of decomposing a raw material gas containing carbon atoms by plasma CVD, thermal CVD or laser irradiation to recrystallize carbon atoms on the surface of a silicon substrate. For example, a method has been used for manufacturing graphene on the surface of a silicon substrate by causing a raw material gas of a compound having carbon and hydrogen to flow on the silicon substrate and generating plasma from the raw material gas by microwave excitation while irradiating the silicon substrate with laser light.
However, in the case of decomposing a raw material gas by plasma or laser light, it is difficult to control the energy applied to each carbon atom because the distribution of energy applied to the carbon atoms decomposed from the raw material gas extends over a wide range. In this case, for example, diamond or DLC (Diamond-Like Carbon) instead of graphene may be generated from the carbon atoms to which excessively high energy is applied, and the carbon atoms to which energy is not sufficiently applied may not be completely recrystallized. Therefore, the graphene thus manufactured contains a carbon bond other than a six-membered ring structure of a carbon atom, and a part thereof becomes amorphous. That is, it is difficult to manufacture a high-quality graphene.